BizTalk under the hood

Johan,

Correct, the BizTalk Host Instances are Windows Services. You’ll notice that when you create a new Host Instance through the BizTalk Admin Console, a corresponding Windows Service (BizTalk Service BizTalk Group : [HOST INSTANCE NAME]) will be created on the target machine.

Hope this helps, Nick.

While Nick is correct, I would also add that the SQL Server Databases, mainly the MessageBox make significant contributions to the overall solution.  If anything SQL Server acts as the “brain” of BizTalk.  The Host instances(or windows services) really process whatever work is set aside for it via the BizTalk Databases.